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Hillsboro's new water system is under construction

The Willamette Water Supply pipeline is one of the most expensive infrastructure projects in Oregon.

As developers work to the lay the foundation for Oregon's largest housing development south of town, a second set of crews have been laboring underground to install one of Oregon's most-costly infrastructure projects.

The Willamette Water Supply pipeline will eventually run from Hillsboro to the Willamette River in Wilsonville, supplying water to Hillsboro customers and the Tualatin Valley Water District, which serves more than 200,000 Washington County customers.

The price tag for the 30-mile pipeline project is around $1.2 billion.

The project will take years to complete, but workers are currently digging a trench for the section of the pipeline slated to pass under Southeast Tualatin Valley Highway and follow Southwest Cornelius Pass Road all the way to Highway 26. On a tour of the site on Monday, a handful of workers in white hard hats scurried around a 48-inch pipe at the bottom of a deep pit south of TV Highway as steel plates plunged into the earth.

A few yards from the pit, a future extension of Cornelius Pass Road winds through the land where 8,000 homes and apartments will be built over the next decade. This is the Reed's Crossing neighborhood, one of the large developments that make up South Hillsboro.

Hillsboro city officials say the pipeline project is not designed to quench the thirst of South Hillsboro, which is slated for completion around the same time as the pipeline. In June, Hillsboro Water Department Director Kevin Hanway told the Tribune the pipeline will supply water to Hillsboro residents for the next 50 years.

The city selected the mid-Willamette project over ideas to raise the level Hagg Lake and purchasing water from Portland, among other options.

"We're building the pipeline before South Hillsboro is built," said Andre Tolme, project manager. The project worked with the Oregon Department of Transportation to reconfigure the intersection of Cornelius Pass and TV Highway to cut down on lane closures, limiting the impact on drivers, Tolme said. The project will also coincide with a county widening project of Cornelius Pass Road north of TV Highway.

This is one of several such worksites along the path of the pipeline. In Sherwood, crews are blasting through a hillside to lay pipeline and extend Southwest 124th Avenue. They've already tunneled under railroad tracks, and are grinding rock for gravel infill used in other portions of the project.

Steve Clapper, a supervisor with the pipeline project, said crews have been blasting to clear some sections of roadway. The blasted rock is reused as roadbed to save on hauling costs.

"We're keeping the material on site," Clapper said.

Here, the pipeline is more than five feet across — tall enough to walk in. Each section of the pipe is 50 feet long, weighing in at 20,000 pounds. The pieces are welded together with the only joints at valve sections, which according to project officials, will have a better chance of withstanding earthquakes.

The majority of the money spent building the project is staying in the Portland Metro area, a major selling point for the project partners. According to project documents, the partners have spent $41.3 million on the project so far. Most of that has gone to 85 local contractors and businesses. Kerr Contractors is working on the 124th Avenue and South Hillsboro projects, the first two portions of pipeline construction.

Looking ahead

Beginning in 2018, crews are scheduled to continue pipeline extension from TV highway to Southeast Frances Street in Hillsboro. Construction from Southwest Farmington Road is set to begin in 2019.

The longest stretch of the pipeline, a 7.7-mile section southwest of Beaverton, runs from Farmington Road south to Bull Mountain, and should begin construction in 2018.

The project also calls for a water treatment plant and pump station, slated for construction in Sherwood beginning in 2022. Storage tanks will be built near Cooper Mountain Nature Park in Beaverton beginning in 2022, and along with the treatment plant, are among the final scheduled portions of the project set to wrap up in the first quarter of 2026.

Tolme said the project doesn't call for a new intake facility on the Willamette River. The project can simply expand portions of the current facility, which is located just upriver of the Interstate 5 crossing in Wilsonville.